This invention relates to a container unloading system for gravity unloading of particulate lading or material at an unloading site, and more particularly to an apparatus and method for a container unloading system for the unloading of particulate lading from a container at the unloading site upon upward tilting of the front end of the container.
Particulate loadings, such as polycarbonate or thermoplastic materials, synthetic resins, for example, are normally loaded within boxes, bags, containers or the like at the site where the polycarbonate plastic material is manufactured, and then transported by wheeled vehicle to a site where the plastic material is unloaded from the container into a storage facility for subsequent use in the manufacture of various plastic end products. It is highly desirable that such plastic materials or ladings, such as polyethylene pellets, not be contaminated by foreign matter or the like as even small amounts of foreign matter or contamination affect the quality of the subsequent manufactured products. Heretofore, plastic liners or bags such as vinyl or polyethylene liners have been used within containers to protect the lading from contamination. The plastic liners are normally sealed at the initial loading site and the lading is maintained in sealed relation within the plastic liner until unloaded at the unloading site, thereby insuring that the plastic lading will not be contaminated. Normally, the plastic lading is unloaded at the unloading site from the container by a suction or vacuum line extending within the container and then is conveyed pneumatically to a storage facility, such as bins, silos, or the like, until needed for the production of plastic end products. Pressurized air is sometimes used to push or aid in pushing the particulate material into the storage facility.
Heretofore, such as shown in U.S. Pat. No. 4,875,811 dated Oct. 24, 1989, U.S. Pat. No. 5,096,336 dated Mar. 13, 1992 and U.S. Pat. No. 5,378,047 dated Jan. 3, 1995, a container has been used in intermodal transportation by mounting on railway flat cars, container ships, or highway trailers, for example, for the transport of particulate material with the particulate material being sealed in a flexible bag within the container and then unloaded at an unloading site by tilting of an end of the container. The transportation system illustrated in U.S. Pat. No. 4,875,811 transports particulate material in a sealed condition from one location or site where the particulate lading is loaded into a container having a liner or bag therein, to another location or site where the sealed liner or bag within the container is broken for unloading of the particulate lading from the container into a storage area. Such a system is utilized also for the transport of other various particulate materials, such as, for example, granular or powdered materials used in foodstuffs.
The container after being loaded and sealed at the first site is transferred to a tiltable container support frame on a highway vehicle for transport to the second site where the sealed container is broken and then tilted by a tiltable support frame to an angle above the angle of repose of the lading within the container for discharge of the lading by gravity from the container into a pneumatic discharge line for pneumatic conveying to a suitable storage facility, such as a storage bin or silo.
One end of the container has a pair of rear doors which are normally latched in closed position during transit. The bag fitting between a pair of end bulkheads is filled with lading from a flexible hose extending within an upper tubular inlet extension or neck of the bag. Upon filling of the bag with lading the bag is urged against the end bulkheads and the extending tubular extension is sealed by suitable banding or ties. Thus, the lading is sealed within the bag for transport to an unloading site.
The loaded container as illustrated in U.S. Pat. No. 4,875,811 is then transferred to a tiltable container support frame pivotally mounted on a highway trailer body and is releasably secured thereon for transport by a highway vehicle to an unloading site. At the unloading site, at least one of the end doors of the container is opened and a discharge outlet for the pneumatic conveying apparatus is removably connected adjacent the rear end of the container for unloading of the container. The inner end of the lower tubular extension or spout of the bag is sealed at its juncture with the bag by a sealing membrane defined by the portion of the bag covering the inner end of the lower spout. This sealing membrane must be cut or removed in order for the lading to be unloaded from the plastic bag. Thus, the lading is tightly sealed upon loading within the plastic bag, and the plastic bag remains in a sealed condition until it is opened by slitting the membrane for gravity discharge directly into a pneumatic conveyor through the discharge outlet at the unloading site. The container or the plastic bag is not pressurized in any manner during unloading and the plastic bag collapses as the lading is removed or discharged. Thus, loss of lading after being loaded within the plastic bag in the container until the loading is discharged into the pneumatic unloading system at the unloading site is minimized.
The pneumatic conveying apparatus and the connecting lading conduits between the rear end of the container and the pneumatic conveying apparatus are positioned between the rear end of the container and the rear tandem wheels in order to permit an effective and satisfactory gravity unloading of particulate lading from the rear end of the tilted container to a rotary valve which feeds the particulate lading into an air stream in a lower pneumatic hopper for pneumatic conveyance to a storage site such as a silo, for example.
The rotary valve and a throttling valve together with connecting lading conduits extend between the rear end of the container and the pneumatic conveying conduit below the rotary valve. Thus, a substantial distance of several feet is provided between the pneumatic conveying conduit and the rear end of the container. It is possible that a very small amount of contamination could occur with the passage of lading through the rotary valve and the connecting lading conduits to the pneumatic converging conduit beneath the rotary valve.
It is desired that the particulate material flow from the container directly to the pneumatic conveying conduit in a minimal distance and without passage through a rotary valve which may also at times possibly damage some of the plastic pellets by contact with the vanes of the rotary valve, for example.
The present invention is directed generally to a container unloading system for unloading particulate material from a container removably supported on a highway trailer with the particulate material being stored in a sealed plastic bag within the container. The plastic bag is filled with lading inside a container and the plastic bag is then sealed for transport. The lading may comprise plastic pellets, grain, pellets, foodstuff, or the like. The container has a rear end bulkhead adjacent a pair of rear doors which are opened for unloading of the container. The plastic bag is supported against the rear bulkhead.
The particulate material is unloaded from the plastic bag by gravity upon tilting of the front end of the container to a desired angle, generally greater than the angle of repose of the lading being unloaded. A rear discharge fitting is secured to and extends through an opening in the rear bulkhead to provide a connection for an unloading device upon opening of the rear doors of the container. A removable vacuum unloading device is removably connected to the discharge fitting at the unloading site for the unloading of the particulate material from the container.
The vacuum unloading device which forms an important part of this invention includes a pair of substantially rigid tubular conduits secured to each other in a perpendicular relation and in fluid communication. A first tubular conduit is connected to the discharge fitting on the bulkhead upon opening of the rear doors of the container for receiving particulate material from the container. The other tubular conduit which extends in a horizontal direction transversely of the longitudinal axis of the container is connected to a pressurized pneumatic source for exerting a vacuum on the first conduit to draw particulate material therefrom for conveyance to a suitable storage site. A manually operated butterfly valve member is provided in the first conduit to control the flow of particulate material from the container. Another manually operated control valve is mounted in the pneumatic conduit upstream of the first conduit to control the vacuum and flow of air along the pneumatic conduit.
In order to commence the flow of particulate material from the container, the first conduit has a door movable manually to an open position to permit manual access to the interior of the conduit and the discharge fitting which is adjacent the plastic bag. A workman, upon opening of the door, manually reaches inside the first conduit which is connected to the discharge fitting and then reaches through the discharge fitting with a cutting device, such as a knife, to slit the plastic bag adjacent the discharge fitting. After the bag has been slit or punctured to start the flow of particulate material into the discharge fitting, the workman then withdraws the knife from the interior of the first conduit and closes the door. Then, upon tilting of the container to the desired angle, such as the angle of repose of the particulate material being unloaded, the flow of particulate lading into the conduits of the vacuum unloading device commences controlled by the butterfly valve members on the conduits.
The first conduit extending from the discharge fitting on the rear end of the container to the pneumatic conduit is relatively short and extends a distance less than about two feet. Thus, a small travel distance in a straight direction is provided for the particulate lading when conveyed from the container to the pneumatic conduit. Such a small travel distance practically eliminates any contamination of the particulate material or lading being unloaded and the only valve member or obstruction in the conduit is a butterfly valve member which provides minimal obstruction to the particulate material.
It is the object of the invention to provide a container unloading system for the gravity unloading of particulate material from the container upon upward tilting of the front end of the container in which minimal contamination and damage to the particulate material is provided.
It is a further object of the invention to provide in a dense phase vacuum air conveying system a vacuum unloading device which is removably connected to the rear end of the container at an unloading site and provides a minimal travel distance of the particulate material from the container to a pneumatic conduit for transport.
A further object of the invention is to provide such a vacuum unloading device having a pair of rigid tubular conduits secured to each other in a perpendicular relation with one of the conduits providing manual access to a discharge fitting on the rear end of the container to permit slitting or puncturing of a plastic bag containing the particulate material for commencing flow of the particulate material upon tilting of the front end of the container.
Other objects, features and advantages of the invention will become more apparent after referring to the following specification and drawings.